These are referred to as 'small heated pools' in legislation. Some spa pools are exempt from the Building Act fencing requirements.
Fencing and inspection requirements may apply to your spa pool depending on its size.
If a spa pool's water surface area is less than 5m2, its sides are higher than 760mm above the adjacent floor or ground, and the walls of the spa pool inhibit climbing, then a lockable safety cover (with safety signage) is permitted.
A safety cover must:
Otherwise, an alternative barrier and periodic inspection requirements will apply.